[백준 10828] 스택 - Python

import sys
n = int(sys.stdin.readline())

stack = list()
for i in range(n):

    op = sys.stdin.readline().split()
    if op[0]=='push':
        stack.append(op[1])
    elif op[0]=='pop':
        if len(stack)==0:
            print(-1)
        else:
            print(stack.pop())
    elif op[0]=='size':
        print(len(stack))
    elif op[0]=='empty':
        if len(stack)==0:
            print(1)
        else:
            print(0)
    elif op[0]=='top':
        if len(stack)==0:
            print(-1)
        else:
            print(stack[-1])